Vince Cable has been moved from a key role at a Liberal Democrat rally in favour of the Minister caught up in the party’s ‘sex harassment’ row.

Lib Dem rising star Jo Swinson, the Women’s Minister, has been picked ahead of Business Secretary Mr Cable to address party activists at their spring conference next weekend.

The decision came after party managers demanded a female speaker because next Friday is International Women’s Day.

Vince Cable's spokesman said he was 'perfectly relaxed' about the speaking arrangements, where rising star Jo Swinson will address party activists at next weekend's spring conference

But the move has surprised some Lib Dems who see Mr Cable as one of the party’s biggest hitters and the main potential successor to party leader Nick Clegg.

Ms Swinson, a close ally of Mr Clegg, is also now facing demands to come clean on what she did know about the sex harassment claims – strenuously denied – against ex-Lib Dem chief executive Lord Rennard.

Ms Swinson is facing demands to come clean on what she did about sex harassment claims – strenuously denied – against Lord Rennard

She has been accused of failing to act on previous information about Lord Rennard’s alleged behaviour towards female party members when she was equalities spokesman – a claim she denies.

Last night, some party members feared that the change of speaker, agreed before the sex harassment claims became public, could backfire.

One said: ‘If this was a calculated attempt to clip Vince’s wings, it is not looking very clever now the Rennard row has broken.

‘It’s embarrassing enough that our spring conference coincides with International Women’s Day without the fact we’re “headlining” one of the main party figures caught up in the row.’

Mr Cable’s spokesman said he was ‘perfectly relaxed’ about the speaking arrangements.

The weekend rally in Brighton is set to be a lengthy celebration of the party’s Eastleigh triumph.